Most of the “increase” of the food allergies and childhood mental and physical illness’ are because we now know what they are and there are means of identifying them. Before, they were lived with (or died with) and defined as “slow learner”, “frail child”, “bad behavior”, “problem child” and the like.
Add that everyone is now mainstreamed, our diet is much broader than it ever was, and there are many more of us and you will then see more problems.
All the hoopla on GMOs goes back to when GMO corn was introduced and the bacteria used to modify it was not cut from the corn. It was only one strain of the GMO corn but it caused allergic reactions and was immediately ID’ed and removed. We have had GMO corn for more than ten years with no health problems.
I,like the author, have no scientific proof, but theorize that if you eat GMO food you will add years to your lifespan. Since our lifespan is increasing, it must be true.
Read your sentence again carefully. The actions YOU take might have an impact on YOUR individual lifespan, but one person cannot make a difference in "our lifespans" unless you have a rather small and tightly controlled test group. And do all your figuring after everyone has died. And then average out all the mitigating factors, etc, etc.